Well-logging instruments are used in wellbores to make, for example, formation evaluation measurements to infer properties of the formations surrounding the borehole and the fluids in the formations. Such well-logging instruments may include electromagnetic instruments, acoustic-sonic instruments, and other instruments, for example.
For borehole seismic surveys, multi-level arrays of seismic sensor devices are coupled in series and include receivers sensitive to such factors as velocity, acceleration and pressure. Properties of a seismic wavefield are measured, and it is important to know the location of the sensor, and with a vector measurement, the orientation of the sensor. Thus, the sensor location and orientation should be known. Sensor orientation has been estimated using seismic data and assumptions about energy propagation in the earth from the source to receivers. These borehole seismic arrays discriminate the propagation direction of acoustic and elastic waves. For this reason, the absolute orientation of the seismic sensors is desired. In one example, the borehole seismic arrays include flexible interconnects between the seismic sensors (also termed shuttles), where each seismic sensor rotates independently with respect to others or include stiff bridles that enforce consistent orientation between the sensors, albeit with some unknown long-range torsion. Even with stiff bridles, the absolute orientation of the array remains unknown.